Though 27 states have held congressional primaries, there’s still plenty of action in store. And the biggest batch of must-watch contests is coming next month.

On the docket: a handful of races involving sitting members facing serious challenges and a quartet of member-vs.-member clashes.

Among the races receiving the most attention are veteran Democratic Rep. John Conyers’s battle against several challengers in a reshaped Michigan district. In a GOP slugfest in Florida, longtime Rep. John Mica is up against tea-party-aligned freshman Sandy Adams. Then there’s Republican Rep. Allen West’s primary in South Florida, where the freshman faces a moderate opponent trying to cast the outspoken lawmaker as too controversial for his own good.

Here are the 10 August primaries POLITICO is watching:

Aug. 2

Tennessee: 3rd District

Freshman GOP Rep. Chuck Fleischmann is facing two formidable primary opponents — 25-year-old Weston Wamp, the son of Fleischmann’s immediate predecessor, former Rep. Zach Wamp, and dairy mogul Scottie Mayfield. During the opening fundraising quarter of his campaign, Mayfield took in more than $450,000, outpacing Fleischmann by more than $200,000.

Wamp and Mayfield see Fleischmann as a ripe target after he received just 30 percent of the vote in the 2010 primary. Fleischmann narrowly prevailed over a splintered field that included former Tennessee Republican Party Chairwoman Robin Smith.

Mayfield was hurt early in the contest by news that his son was charged with vandalism for slashing the tires of a Fleischmann campaign staffer.

Aug. 7

Michigan: 6th District

Former state Sen. Jack Hoogendyk is back for a rematch against GOP Rep. Fred Upton after falling short 57 percent to 43 percent against the incumbent in a 2010 primary. This time, Hoogendyk has backup from the anti-tax Club for Growth, which has aired TV ads calling the House Energy and Commerce Committee chairman not conservative enough.

But Upton won’t be easy to beat. The incumbent had more than $2.2 million in cash on hand at the end of March; Hoogendyk had a meager $39,000. And outflanking Upton on the right isn’t a given: Upton, who long had a reputation as a moderate, has repositioned himself as a conservative and strident critic of President Barack Obama.

13th District

Conyers is a Detroit icon — the 83-year-old congressman was elected in 1964, making him the second-longest-serving member of the House.

But the Democrat now finds himself in the toughest reelection fight of his career, forced to run in a newly redrawn district, nearly half of which he hasn’t represented before. His seat was refashioned to include less of Detroit and to take in a wide swath of its suburban areas, which includes a large population of white voters. That’s created an opening for state Sen. Glenn Anderson, Conyers’s leading opponent, who is white and a well-known name in suburban Detroit.

Conyers must contend with four black candidates who threaten to siphon African-American votes. Also not helpful to his cause are lingering memories of a scandal involving his wife, former Detroit City Councilwoman Monica Conyers, who was jailed in 2010 after she pleaded guilty to federal bribery charges.

With his nearly unmatched seniority, Conyers remains the favorite — but it won’t be a cakewalk.

14th District

Rep. Gary Peters has emerged as the early front-runner in his battle against fellow Democratic Rep. Hansen Clarke, raising nearly three times as much cash as his opponent.

Perhaps more surprising, Peters, who is white, has won a batch of critical endorsements from key African-American political figures over Clarke, who is black. Among those who have endorsed Peters, a second-term Democrat, are Detroit Mayor Dave Bing and The Black Slate Inc., a church-based PAC in Detroit. More than half of the voters in the newly drawn district are black.

Clarke, a freshman, must compete for black votes with two other African-American candidates. He also needs to win over supporters of former Rep. Carolyn Cheeks Kilpatrick, the former chairwoman of the Congressional Black Caucus whom he unseated in a hard-fought 2010 primary.

Clarke is also confronting sudden questions about his heritage — specifically whether his now-deceased mother was white rather than black, as he has claimed. Clarke, who has blamed the scrutiny on unnamed opponents, announced last month that he would not participate in more debates. He cited “the use of racist rhetoric and race-baiting by certain candidates in the 14th Congressional District race.”

Missouri: 1st District

Rep. Russ Carnahan faces an uphill slog in his clash with fellow Democratic Rep. Lacy Clay, a race pitting two Missouri political dynasties. Carnahan’s south St. Louis seat was decimated in redistricting, leaving him with little choice but to run against Clay in a district Clay has represented far more of.

Carnahan, who is white, is also at a disadvantage because around half of the voters in the district are black. Clay, who is African-American, has begun airing radio ads touting his support from pastors.

Aug. 14

Florida: 18th District

Bob Crowder faces a herculean task in the Republican primary: defeating Allen West, a tea party heartthrob and fundraising machine.

But Crowder, a Martin County sheriff, does have one advantage: the district is largely unfamiliar to West, who decided earlier this year to move from a neighboring Democratic-friendly seat to run for the more Republican-oriented 18th District.

Crowder is painting the freshman congressman as too extreme and was recently quoted calling the congressman “offensive.” Crowder, who supported Democrat Alex Sink in the 2010 Florida gubernatorial contest, has billed himself as a moderate.

West, who has raised an astonishing $7.6 million to Crowder’s paltry $26,000, is ignoring his challenger’s call for a debate. “Instead of demanding a debate, my primary opponent would be better served by studying up on the issues and getting in touch with people he wants to represent,” West wrote in a recent editorial.

7th District

Adams faces an uphill battle in her primary race against Mica, a well-known commodity in northeastern Florida politics who has more than double her cash.

Still, the incumbent-vs.-incumbent faceoff has the makings of a bare-knuckled affair. Adams is pitching herself as a tea-party-aligned, fresh-faced conservative while criticizing the 69-year-old Mica as a past-his-prime, prolific earmarker.

Adams, who has represented more of the newly drawn district than Mica, has begun racking up endorsements from conservatives, including longtime activist Phyllis Schlafly.

Aug. 28

Arizona: 4th District

Rep. Paul Gosar has emerged as a prime target for Republicans looking to wage a primary campaign against him. The congressman has raised just $687,000 since winning election in 2010 — a paltry sum for a sitting member — and is running in a northern Arizona district that is mostly new to him.

The freshman had been drawn into the 1st District, where he would have faced a tough rematch against former Democratic Rep. Ann Kirkpatrick but instead chose to run in the more Republican-friendly 4th District.

Gosar’s lead opponent is state Sen. Ron Gould, who has struggled with fundraising but has won the support of conservative groups including the Club for Growth and FreedomWorks.

6th District

The clash pitting freshman GOP Reps. Ben Quayle and David Schweikert is seen as an establishment vs. tea party battle, with Quayle winning an endorsement from Sen. Jon Kyl and Schweikert scoring the support of FreedomWorks.

And it’s gotten personal: Schweikert has begun hammering Quayle over his alleged past contributions to a website that chronicles Scottsdale’s nightlife. Quayle has accused Schweikert of sending a spy to his campaign headquarters.

The two are also trying to claim the conservative label. Last month, the two introduced competing immigration legislation designed to block President Barack Obama’s newly announced policy to stop deporting young illegal immigrants.

2nd District

Democratic Rep. Ron Barber has been in office for less than a month, yet he’s already inflamed liberals in his southern Arizona district.

Barber, who won a June 12 special election to finish out the term of former Democratic Rep. Gabrielle Giffords, has sided with Republicans on two key votes recently — one to allow Border Patrol agents to circumvent certain environmental laws, and then to hold Attorney General Eric Holder in contempt of Congress.

Heinz is still the underdog — Barber was elected comfortably, and there’s residual goodwill toward him because of his work for Giffords. But Heinz has found two issues to fuel his campaign.

CORRECTION: A previous version of this story misstated the results of the 2010 race between Jack Hoogendyk and Fred Upton and the district number of the Arizona primary between Matt Heinz and Ron Barber.